1. Field of the Invention
The present invention relates to an electromagnetic fuel injection valve, and particularly to an electromagnetic fuel injection valve in which a magnetic cylindrical body which constitutes a part of a valve housing having a valve seat at a front end portion is connected to a front portion of a cylindrical fixed core via a coaxial non-magnetic cylindrical body; a solenoid housing comprises a cylindrical magnetic metal coil case integrally having, at one end side, a ring-shaped end wall portion and a press-fit cylindrical portion integrally connected to an inner periphery of the end wall portion so that the magnetic cylindrical body is press-fitted to the press-fit cylindrical portion and the press-fit cylindrical portion is welded to the magnetic cylindrical body, and a flange portion which protrudes radially outward from a rear end of the fixed core and is magnetically connected to the other end of the coil case; a coil assembly which surrounds a rear portion of the magnetic cylindrical body, the non-magnetic cylindrical body and the fixed core is housed in the solenoid housing; and at least the solenoid housing is covered with a resin molded part made of a synthetic resin and integrally having a power receiving coupler which faces a power-receiving-side connecting terminal connected to a coil of the coil assembly.
2. Description of the Related Art
Such an electromagnetic fuel injection valve is already known from, for example, Japanese Patent Application Laid-open No. 2004-76700 in which a coil case 31 made of magnetic metal is formed as shown in FIG. 4. Specifically, in forming a coil case 31′ integrally having, at one end side, a ring-shaped end wall portion 31a and a press-fit cylindrical portion 31b′ connected to an inner periphery of the end wall portion 31a, a magnetic-metal bottomed cylindrical material 65 having a dish-shaped projecting portion 65a at a central portion of a closed end and is formed of is prepared, and punching is performed by a punch 66 and a die 67 to punch out the central portion of the closed end in the material 65 as shown in FIG. 4(a), thereby obtaining the coil case 31′ as shown in FIG. 4(b).
The press-fit cylindrical portion 31b′ has a function of exchanging magnetic flux with the magnetic cylindrical body by press-fitting therein the magnetic cylindrical body and being welded to an outer periphery of the magnetic cylindrical body, and needs to secure a predetermined length or more for close contact with the outer periphery of the magnetic cylindrical body. When the coil case 31′ is formed by the above described punching, a portion incapable of coming into close contact with the outer surface of the magnetic cylindrical body is generated in a tip end side of the press-fit cylindrical portion 31b′ over a comparatively long distance L1 due to formation of a shear drop and a fracture surface. In order to secure a contact portion with the outer periphery of the magnetic cylinder over a predetermined length or more, a total length (L1+L2) of the press-fit cylindrical portion 31b′ becomes large. When the press-fit cylindrical portion 31b′ becomes long in this way, the resin molded part covering the solenoid housing also becomes long, so that the projecting amount of the valve housing from the resin molded part becomes short. As a result, when the fuel injection valve is mounted to a passage forming member which forms an intake passage, the exposed length of the valve housing to the intake passage side becomes short, unless the electromagnetic fuel injection valve is increased in size, and therefore injected fuel may easily attach to an inner surface of the intake passage.